Developing a Shewhart chart. The accounting department is instituting process improvement and has been studying causes of delays, rework, and excess overtime. The department’s quality control charts indicate that a large number of invoices have to be manually handled (requiring extra phone calls, rerouting documents, and other types of rework) because of mistakes or incomplete information on purchase orders. The head of the accounting department has asked the manager of the purchasing department to investigate this problem.

The purchasing manager decided to select some of the prepared orders for each purchasing agent over a one-week period and review them for completeness and errors. Sixty documents were randomly selected from the work of each of the 20 agents and were reviewed.

Orders with one or more mistakes were identified. The following data were obtained at the end of the week:

(a) Develop a Shewhart chart for these data.

(b) What can the purchasing manager learn from these results?

(c) Are the mistakes due to special or common causes?

(d) Which agents should be selected for special consideration?

(e) What feedback should the manager give to the head of the accounting department?

(f) Should the purchasing manager continue to collect data? If so, how should he analyze the data?
(g) What other types of data would be useful?
(h) Plan the next sequential PDSA to build on the learning in this cycle.

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Number of orders Number of orders Agent with mistakes Agent with mistakes Dan 5 Bart 4 Hank 0 Linda 1 Ann 2 Judy 3 Bill 6 Helen 9 Mary 7 Larry 8 Dave 5 Ron 4 Fred 8 John 5 Sue 4 Mark 0 Chris Tom 05 Emma 6 Tina 8